The use of emergency vehicle signal devices for increasing the visibility of public service vehicles is well known in the art. Vehicles using such devices include emergency, police, municipal, and construction vehicles, among others. The most widely employed type of visual warning system is the roof-mounted light bar. Such a light bar includes a plurality of light generators arranged on a support that spans from side-to-side, and either rests upon or is spaced above, the roof of the emergency vehicle. While such light bars accomplish the purpose of producing a wide variety of highly visible light radiation patterns to warn the public of the presence of an emergency vehicle, prior art light bars possess certain inherent disadvantages. For example, such prior light bars tend to increase vehicle wind resistance, increase fuel consumption and produce turbulence that results in interior noise at high speeds. A traditional light bar also increases vehicle height, which may limit access to certain areas, or present the possibility of damage to property or the light bar itself where there is limited overhead clearance. Arguably the most significant drawback to a roof-mounted light bar in the context of law enforcement vehicles is that the presence of a light bar conspicuously identifies the nature of the vehicle.
The prior art discloses aerodynamic light bars, low profile light bars and light bars mounted against the inside of vehicle windows that address some of the disadvantages of traditional roof mounted light bars. Other alternative configurations include various combinations of grill or bumper-mounted warning lights, headlight flashers, warning lights mounted inside the vehicle on the dashboard, sun visors or rearview mirror, and warning lights integrated with the externally mounted rearview mirrors. With respect to warning lights placed inside the vehicle, vision at night can be problematic, due to reflection of the light into the interior of the vehicle.
Another approach to providing an inconspicuous warning light is to place a strobe warning lamp in the reflector shells for the front and rear corner signal/running lamps. This has typically been accomplished by drilling a second opening in the reflector and installing a strobe base and bulb to project into the shell. One drawback of this procedure is the need to modify parts of the vehicle. Further, the strobe lamp cannot be arranged at the focus of the reflector and is thus rendered significantly less effective in its warning function. Strobe-type lamps are known to be relatively short lived and require frequent maintenance.
The use of LED's in warning and signaling lights is well known. Older models of LED's produced limited quantities of light over a relatively narrow viewing angle centered around an optical axis of the LED. These LED's were typically massed in compact arrays to fill the given illuminated area and provide the necessary light output. Modern LED's produce significantly greater luminous flux per component, permitting fewer LED's to produce the luminous flux required for many warning and signaling applications. It is known to arrange a small number of high-output LED's in a light fixture and provide each high-output LED with an internally reflecting collimating lens. The collimating lens gathers light from the LED into a collimated beam centered on the LED optical axis. Such an arrangement typically does not fill the light fixture, resulting in an undesirable appearance consisting of bright spots arranged against an unlit background. Light-spreading optical features on the outside lens/cover are sometimes employed to improve the appearance of the light fixture.
There is a continuing need for a new and improved emergency vehicle signal light that provides high visibility for an emergency vehicle while overcoming the disadvantages discussed above. The emergency vehicle light is preferably energy efficient and requires little or no maintenance.